Indoor Air Comfort Research Articles

Impact of natural ventilation and outdoor environment on indoor air quality and occupant health in low-income tropical housing

Ventilation is pivotal in mitigating indoor pollutants and ensuring comfortable Indoor Air Quality (IAQ) levels globally. The outdoor environment and ventilation mechanisms significantly impact indoor air quality and occupant health. This research investigated the impact of natural ventilation (NV) and outdoor environment (OE) on indoor air quality (AQ) and occupant health (HI) in low-income housing in Kampala City, Uganda. The study followed a mixed methodology approach by employing self-administered questionnaires and statistical modeling using IBM® SPSS® Amos V24 to analyze the relationships between Natural Ventilation (NV), indoor Air Quality (AQ), Outdoor Environment (OE), and occupant health (HI). The research reveals a strong correlation (0.76) between NV and AQ. In contrast, correlations between AQ and OE (0.16) and NV and OE (0.08) are weak. Model comparative fit indices (CFI: 0.984, SRMR: 0.029, RMSEA: 0.053) indicate an excellent fit. Reliability is high with Cronbach's alpha (NV: 0.800, AQ: 0.862, OE: 0.782) and AVE values (NV: 0.832, AQ: 0.869, OE: 0.786). Significant positive relationships were found between NV and AQ and AQ and HI, highlighting the importance of natural ventilation in improving indoor air quality and occupant health. The study supports SDGs 3, 11, and 13, promoting sustainable building practices and promoting health, enhanced living conditions, and lower greenhouse gas emissions.

Assessing indoor air temperature settings in residential buildings during the COVID-19 era

While comfort models provide reliable evidence for designing building thermal environments, they may not be adequate for assessing building energy consumption due to factors beyond comfort. These factors influence occupants' actual control of their thermal environment. This study assessed how residential building occupants control indoor air temperature to maintain their comfort during the COVID-19 era. A dataset established from the ‘Donate Your Data’ program administered by Ecobee Inc. was utilised. The dataset was collected from 86,658 thermostats belonging to 65,535 users in the United States over multiple years, along with metadata that includes characteristics of the users and their homes. Statistical analysis was performed to suggest an indoor temperature range at which 90 % of collected data falls when the prevailing mean outdoor air temperature is between −10 °C and 37 °C, which effectively covers a wide variety of climate conditions. The estimated range of indoor air temperatures was 6.3 K before the pandemic, but it decreased by 1 K–5.3 K during the pandemic, implying that occupants used more energy to maintain a comfortable indoor air temperature during the pandemic. Our model can be useful in designing indoor temperature settings in residential buildings based on outdoor temperature.

Uncertainty modelling in the selection of climate control system manufacturers for preconstruction of hydroelectric power plants

Heating, ventilation, air conditioning, and refrigeration systems, the critical intersection point of low environmental impact, neutral thermal comfort and acceptable indoor air quality are technologies that directly affect the electricity generation of hydroelectric power plants on the axis of sustainability. Addressing challenges in decision-making for pre-construction system selection, this study employs fuzzy set theory, specifically Pythagorean and q-Rung Orthopair fuzzy sets, to model uncertainty in hydroelectric power plant specific considerations. Utilizing Analytic Hierarchy Process, Technique for Order of Preference by Similarity to Ideal Solution and the Complex Proportional Assessment the model evaluates ten global climate control system manufacturers. Sensitivity and comparative analysis ensure result validity, offering valuable insights for industry professionals and decision-makers, streamlining the complex process of selecting the most suitable manufacturer.

Multi-priority HVAC temperature control with resource constrained based on coordinated distributed zone MPC

The conventional HVAC system for multi-area buildings includes both centralized and in-situ equipment to collectively regulate indoor air temperature to meet the preferences of its occupants. However, due to the limited capacity of the total supply air mass rate in centralized equipment, maintaining comfortable indoor air temperature for all areas can face conflicts. The first conflict arises between satisfying diverse preferences and limited global resources, while the second conflict is between centralized air supply and distributed regulation. In this paper, a distributed zone model predictive control (DZMPC) with priority conflict resolution is proposed for the multi-area HVAC systems. This strategy is composed of a zone parameter optimization with dynamic priority as a coordinated upper layer and a lower DZMPC layer. In the upper layer, a zone parameter optimization with priority is presented to coordinate sub-controllers by adjusting variable references’ bounds for DZMPC, to solve the resource competition when it occurs. In the lower layer, model predictive control with zone control is formed to mitigate the tension of the shared resource. By integrating dual decomposition and Augmented Lagrange function to address global constraints, a distributed solvable control structure is formed. The resulting optimization can be solved using a distributed primal–dual algorithm. The effectiveness of the proposed scheme is proved by simulation examples.

Numerical study on thermal performance of a building design integrating two passive Trombe walls

ABSTRACT This paper deals with a numerical simulation of the transient thermal behaviour of Trombe walls. The temperature fields and velocity distributions are investigated in different components of a test room, in the climate of Lille- France, during two different seasons in order to provide a thorough comprehension of the potential of the Passive Trombe wall. The governing equations are solved by the Finite Volume Method using the CFD software scSTREAM V2020. The numerical results agree well with the available experimental data. The results indicated that the temperature values at the upper vents were always higher than those retrieved from the lower vents forming an air circulation in the space which promotes a comfortable indoor air temperature. Besides, other parameters such as the thickness of Trombe wall, vents dimensions and air gap thickness, are studied to inquire their influence on the Trombe wall’s performance. It is found that the Trombe wall should be constructed with middle thickness with smaller air gaps to enhance thermal comfort in a building. This investigation can be a good reference for Trombe wall design and a valuable insight into the development of a high-efficiency solar air heating system.

Novel wall-attached multidirectional jets: Mathematical formulation, CFD modeling and experimental validation

Achieving a healthy and comfortable indoor air environment has long been an objective of human endeavors. For a novel ventilation system, the wall-attached multidirectional jet pattern, the mathematical model describing the jet trajectory, temperature and velocity changes was first proposed to predict airflow attachment and separation moments from walls, covering a densimetric Froude number range from 0.5 to 4.0. Subsequently, this mathematical model was solved using a comprehensive numerical methodology and validated by full-scale experiments, which demonstrated that this established model could accurately depict the wall-attached multidirectional jet flow, with controllable errors — 16.4% for jet trajectory and 8.2% errors for jet axis temperature — when maintaining a supply velocity of 0.2 m/s. Also, the flow characteristics within a room featuring internal heat sources were analyzed, varying air supply velocities from 0.1 to 0.8 m/s and jet angles from 0° to 60°. Finally, this flow pattern of the wall-attached multidirectional jet was further confirmed and reproduced through CFD modelling which illustrated temperature stratification ranging from 18.1 °C to 25.2 °C, similar to the pattern observed in displacement ventilation. Present research could be valuable for the development of wall-attached multidirectional jet and the establishment of a healthy indoor air environment in practical applications.

The Predicted Performance of Natural Ventilation Strategies in Islamic Boarding School Design in Magelang

The importance issue in providing comfortable indoor air quality conflicts with the use of energy for mechanical cooling in tropics region such as Indonesia. Natural ventilation is seen as a potential to provide comfort through the change of air within the inside and outside of the space. Natural ventilation becomes a strategy to achieve building resilience towards climate change because it requires no energy consumption. Therefore, this research aims to justify the design of natural ventilation of low-income Islamic Boarding School in Magelang using steady state simulation. The results indicated that among three ventilation strategies simulated in this study, it can be concluded that stack effect is predicted to produce higher air flow rate which results to comfortable predicted observation on adaptive comfort.

Evolution of coalescent agent-free ultra-low VOC paint with formaldehyde capturing properties

The majority of people spend a significant portion of their waking lives indoors, they are continually exposed to a higher concentration of indoor air pollutants. As new technologies emerge and more people become aware of the issue, it has become crucial to discover new methods for cleaning up polluted indoor air and minimizing people's exposure to it.This research aims to develop a waterborne, low-VOC, formaldehyde-capturing formulation for interior paint. In paint formulation, biocides, coalescing agents, ammonia, binders, and liquid phase additives are all possible sources of volatile organic compounds. In this study, formulations of coalescing agent-free and formaldehyde-free waterborne coatings with high performance characteristics and ultra-low VOC content were created by chemically adsorbing formaldehyde using an active ingredient. The colorimetric method, which is developed based on the color concentration change, and the cabin method test methods, which monitor the change of formaldehyde concentration in the interior environment, were developed within the scope of the study in order to test the effect of the product. The final formulation complies with the A + French VOC labeling and the Indoor Air Comfort Gold criteria for VOC emissions, and tests demonstrated an 87% decrease in ambient formaldehyde concentrations within 24 h of application (ISO 16000–9:2006, EN 16516:2017).

실내 이산화탄소 농도 예측 기반 적응형 환기 제어 알고리즘 개발

Purpose: This study aimed to develop an adaptive ventilation control algorithm for occupant-centric control (OCC). The control algorithm utilizes a real-time indoor carbon dioxide concentration prediction model that reflects occupant information and is continuously updated through daily learning. Method: The prediction model was developed using a long short-term memory (LSTM) learning algorithm based on data obtained from a living lab. The indoor CO2 concentration after 5 minutes was predicted through the data of the past 1 hour, and the prediction accuracy was evaluated with the test data. The adaptive ventilation control algorithm, which incorporates the prediction model, was then applied to the living lab for experiments to evaluate its real-time prediction accuracy, adaptability, and control performance. Result: As a result of the performance evaluation of the predictive model, the coefficient of variation of the root mean squared error (CVRMSE) was 1.78% and the R2 was 0.97. The adaptability evaluation over four days presented an improvement in CVRMSE from 1.78% to 1.13%, which is approximately 36.52% improvement from the initial performance. During the experiment with the adaptive ventilation control algorithm, the accuracy decreased slightly with a CVRMSE of 2.90% and R2 of 0.98, likely due to frequent ventilation control leading to large data variations. Despite short period of the indoor carbon dioxide concentration exceeding 1,000 ppm, the control was effective. According to the results, it is expected that providing comfortable indoor air quality at all times can be achieved by improving the optimal control cycle and supplementing data learning for various control modes in future research.

Modelling energy performance of residential dwellings by using the MARS technique, SVM-based approach, MLP neural network and M5 model tree

Several previous studies indicate that the energy consumption of buildings has increased steadily during the last decades all over the world. Residential dwellings in European countries are lawfully required to meet the suitable minimum needs concerning energy efficiency according to the European Directives. Specifically heating, ventilation and air conditioning (HVAC) devices represent most of the energy use in dwellings as they have a principal purpose in controlling the inner climate. Hence, one manner to relieve the constantly growing request for supplementary energy supply is to carry more efficient dwelling designs from the energy point of view, which is to say, with superior energy conservation properties. In this sense, an accurate estimation of the heating load (HL) and cooling load (CL) is needed to calculate the detailed descriptions of the heating and cooling device needed to support comfortable indoor air conditions. The goal of this investigation was to acquire some foretold models to achieve a tangible calculation of the HL and CL (output variables) as a function of 8 specific input variables (concretely, relative compactness, surface area, wall area, roof area, overall height, orientation, glazing area and glazing area distribution) at residential dwellings. These eight input factors have been often employed in the literature about the energy performance of dwellings (EPB) to analyse energy-related themes in dwellings. Moreover, a support vector machines (SVM) approach with distinct kernels, an artificial neural network (ANN) of multilayer perceptron network (MLP) kind and M5 model tree were adjusted to the observed data for evaluation of differences. The outcomes of the current investigation are two-fold. First, the importance (or strength) of each input variable on the HL and CL (output variables) is presented through the MARS model. Secondly, the MARS-relied approximation was the most excellent predictor of the EPB. Indeed, a MARS regression was conducted and coefficients of determination equal to 0.9961 for the HL estimation and 0.9651 for the CL estimation were gotten when this approach was employed to 768 diverse residential buildings, respectively. The concordance between the observed data and those predicted with the MARS approximation verified the satisfactory performance of the latter. Finally, the conclusions of this original investigation are summarised.

Feasibility of applying an electrostatic precipitator integrated with a naturally ventilated double-skin façade in residential buildings

One of the main advantages of applying a double-skin façade (DSF) is allowing natural ventilation. As concerns about high outdoor particle concentrations increase, maintaining comfortable indoor air quality through natural ventilation in buildings with DSFs becomes difficult. An electrostatic precipitator (ESP) integrated with a DSF (EPID) has been proposed for maximizing the natural ventilation in buildings with polluted outdoor air. In this study, the particle removal performance and ozone generation of the EPID were experimentally evaluated to determine the feasibility of applying it in residential buildings. An EPID prototype was constructed, and laboratory experiments were performed to measure the single-pass particle removal efficiency and concentration of ozone, a byproduct of the ESP. The results showed that the average particle removal efficiency (77.4 ± 5.5%) at the upper ESP position is similar to that at the lower ESP position (78.5 ± 11.6%) for 0.25–1.82 μm particles at 9 kV applied voltage and 0.5 ms−1 inlet air velocity. When the inlet air velocity increases to 2.0 ms−1, the particle removal efficiency decreases to 39.7% depending on the ESP position. Moreover, the ESP position significantly influences the particle removal efficiency because it changes the inlet air velocity, especially at low applied voltages. Our results highlight the importance of determining the appropriate ESP position in the EPID for residential applications because low-voltage operation is recommended for the safety of occupants and reduction in ozone generation. In addition, at 0.5 ms−1 inlet air velocity, at which the EPID has excellent removal performance, the net ozone concentrations are 33.0 ppb and 35.7 ppb at 6 kV and 9 kV, respectively, which are all lower than the threshold (50 ppb), regardless of the ESP position. The results of this study verify the feasibility of applying the EPID and have important implications for future EPID designs and developing control strategies to improve the indoor air quality of naturally ventilated residential buildings with DSFs.

Individual thermal comfort differences in a Japanese condominium

Thermal comfort and sensation for each person might be different and varies despite being exposed to the same indoor environment due to the differences of their physiological factors such as gender and age. Thus, it is more challenging to provide suitable thermal environment that can satisfy each individual in the building or in the same dwelling. However, only a few studies pursue and focus on investigating the effect of physiological factors on individual thermal comfort perception. A field measurement was conducted in a condominium from September 2015 until October 2016. The measured indoor air environment in each 46 selected dwellings and 17,026 votes from thermal comfort survey for each individual person involved were collected. Therefore, this study aims to examine the variation of indoor thermal environment and determine the factors for the differences in individual thermal comfort. Hence, we categorized the individual from all selected dwellings into several groups depending on the gender and age. The results showed that there is a variation of comfort indoor air temperatures. Thus, these results can be important in designing guideline for each type of building as different user groups most likely to have different expectation regarding indoor thermal environment.

Effect of Indoor Environment on Occupant Air Comfort and Productivity in Office Buildings: A Response Surface Analysis Approach

Indoor air quality is a significant factor influencing occupant comfort, health and productivity. Indoor air comfort and its relationship to occupant comfort and productivity are widely documented. Statistical correlation between the two has been highlighted in scientific literature. This paper investigates any unique correlations between non-air quality parameters (such as lux level, temperature, and noise level) and indoor air comfort and presents a study investigating the effect of indoor environmental quality on occupant air comfort and productivity. This study was conducted by collecting data on indoor environmental parameters using remote sensors and an online survey for occupant responses for twelve months. Data analysis was performed using Response Surface Analysis to present mathematical relationships between indoor environmental quality parameters and occupant air comfort. Results show that carbon dioxide up to 600 ppm, VOC up to 25% (by volume) and humidity up to 60% have a positive impact on occupant air comfort and productivity. Our research highlighted that some non-air quality parameters, such as outdoor temperature and lux levels, affect occupant air comfort. These results would enable built environment professionals to design and operate offices (subtropical desert climate) conducive to occupant comfort and productivity.

Prediction and optimization of thermal comfort, IAQ and energy consumption of typical air-conditioned rooms based on a hybrid prediction model

HVAC systems provide satisfactory indoor environments, but they usually consume large amounts of energy in order to achieve an acceptable thermal comfort level and indoor air quality (IAQ). Balancing thermal comfort, IAQ, and energy consumption is thus a challenging task. However, the main problem faced in such research is that it is inefficient to conduct traditional experiments or numerical simulation to obtain the optimal air supply parameters from a large number of variables. Therefore, the aim of this study is to develop a rapid prediction and optimization framework of IAQ, occupant comfort, and energy consumption. Firstly, Building Information Modeling (BIM) technology and Computational Fluid Dynamics (CFD) simulations are used to create the database containing indoor velocity, temperature and CO2 concentration for different distributions of occupants and ventilation parameters. Next, the extreme learning machine (ELM) model optimized by the grey wolf optimizer (GWO) algorithm is developed to predict the thermal comfort level and CO2 concentration, and the input parameters of the prediction models are interpolated to generate more cases. Finally, the satisfied air supply parameters for various optimization objectives are determined by combining the predicted PMV value and CO2 concentration with the energy consumption analysis. The results of the comprehensive analysis showed that the average concentration of CO2 after optimization is reduced and the |PMV|avg is reduced to less than 0.5, which is within acceptable limits. In addition, 14.34% energy saving is achieved in the illustrative example.

Formulasi Indeks Kenyamanan Udara dalam Ruang pada Tempat Ibadah

Two main functions of public facilities are providing services to residents and maintaining environmental quality. There is currently no index that states the parameters of indoor air comfort quantitatively for worship buildings. The comfort for a building will affect the physical and mental health of its occupants. The research has identified and formulated an indoor air comfort index for worship buildings based on temperature, noise, odour, relative humidity, and light intensity that can be the best recommendations for district/city governments. The research has conducted using qualitative and quantitative methods. The qualitative method is based on filling the questionnaires by respondents and the quantitative method is based on the measurement of five parameters at the research site. The formulation obtained from the results of the weighting of the questionnaire and the index for each parameter. The indoor air comfort index is obtained based on five levels: uncomfortable, less comfortable, quite comfortable, comfortable, and extremely comfortable. The results of the research place of worship gave an index value of 4.0 at Tridharma temple that has declared comfortable, an index value of 2.9 at Church of Immanuel that have declared quite comfortable, and a range of index values of 3.1-3.8 at seven other sites that has declared comfortable.

Experimental performance of a three-fluid desiccant contactor using a novel ionic liquid

• Novel Ionic Liquid that is not corrosive to aluminum is used as liquid desiccant. • New three-fluid fin-tube desiccant contactor fabricated using aluminum. • Experimental performance of the fin-tube contactor using IL solution is investigated. • The fin–tube contactor showed superior performance than the packed bed contactor. • Lower solution flow rates and pumping power is expected using the fin–tube contactor. The experimental performance of a new three-fluid fin–tube contactor using a novel ionic liquid desiccant solution is investigated and compared with those of an adiabatic packed bed contactor with LiCl solution for liquid desiccant air conditioning system applications. Owing to the compatibility of the ionic liquid solution with aluminum, a fin–tube contactor is manufactured to exploit internal cooling from a third fluid. The results indicate the superior dehumidification performance of the fin–tube contactor, which yielded an outlet air humidity ratio of 10.5 g w ·kg da -1 at a solution mass flux of 3.06 kg·m −2 ·s −1 , as compared to a similar humidity ratio at a solution mass flux of 4.98 kg·m −2 ·s −1 achieved by the packed bed contactor. In terms of cooling performance, the outlet air temperature of the fin–tube contactor is 21.9 °C, which is lower than that of the packed bed contactor even at its highest solution mass flux. This indicates that the cooling performance of the fin–tube contactor has minimal dependence on the solution mass flux in achieving cooling effect, owing to the cooling medium flowing inside the tubes. Relatively lower solution pumping power than that of the packed bed contactor can be expected from the fin–tube contactor, in addition to the ability to achieve comfortable and hygienic indoor air at a cooling medium temperature of 17 °C or higher, the ionic liquid desiccant and three-fluid fin–tube contactor pair for liquid desiccant air conditioning system is elevated a step higher as an alternative to vapor compression air conditioning system.

Experimental assessment of thermal comfort and indoor air quality in worship places: The influence of occupancy level and period

Worship places represent a unique type of buildings due to their functionality, dense occupancy, intermittent use, roof geometry, large inner space, and consumed energy of cooling/heating systems. In addition, thermal comfort and indoor air quality are decisive keys that affect the psychological and physiological conditions of occupants as well as their activity level and working efficiency. Though, a scarce number of studies focused on investigating the indoor conditions of worship places. Thus, a mosque located in Bahrain was selected to examine the influence of the occupancy level and period on thermal comfort sensation and indoor air quality. The readings of air temperature, humidity, air velocity, and CO2 concentration were recorded during real several occupancy levels and periods during the summer season. The measured findings of PMV and PPD metrics indicated that the social distancing between worshippers, during the SARS-CoV-2 pandemic, causes a feeling of coolness under the existing cooling system. Meanwhile, the 2-h occupancy period produced a 75% increment of CO2 concentration, 55% during 1-h occupancy, and 20% during half an hour occupancy. Therefore, the air-conditioning systems of worship places should be reconsidered in terms of ventilation rates and partial operating to provide comfortable conditions that accommodate different occupancy levels and periods.

Study on the hygroscopic performances of poplar wood fiber biomass brick

Poplar fiber biomass brick is an energy-saving and environmentally friendly biomass building material developed in recent years. It has good hygroscopic performance, can adjust indoor air humidity, helps reduce building energy consumption for dehumidification and humidification, and improves indoor air comfort. This paper studies the hygroscopic performance of poplar fiber brick from the microscopic pore structure experiment, nitrogen physical adsorption experiment, equilibrium moisture content experiment, moisture sorption and desorption cycle experiment, and water vapor transmission experiment. The model of the sorption-desorption curve of poplar fiber biomass brick at 23 °C is established. Moreover, the ideal moisture buffering value (MBV) of poplar fiber brick and the ideal and practical MBV values under the experimental procedures of this article are calculated. The results show that the Peleg model is most suitable for poplar fiber brick's moisture absorption and desorption curve at 23 °C. The MBV value is the “Excellent” level and has good moisture sorption and desorption performance. The obtained data and models provide potent data support for promoting and applying biomass bricks and theoretical model research.

Indoor Air Quality Control Using Backpropagated Neural Networks

Providing comfortable indoor air quality control in residential construction is an exceedingly important issue. This is due to the structure of the fast response controller of air quality. The presented work shows the breakdown and creation of a mathematical model for an interactive, nonlinear system for the required comfortable air quality. Furthermore, the paper refers to designing traditional proportional integral derivative regulators and proportional, integral, derivative regulators with independent parameters based on a backpropagation neural network. In the end, we perform the experimental outputs of a suggested backpropagation neural network-based proportional, integral, derivative controller and analyze model results by applying the proposed system. The obtained results demonstrated that the proposed controller can provide the required level of clean air in the room. The proposed developed model takes into consideration international Heating, Refrigerating, and air conditioning standards as ASHRAE AND ISO. Based on the findings, we concluded that it is possible to implement a proposed system in homes and offer equivalent indoor air quality with continuous mechanical ventilation without a profuse amount of energy.

Feasibility of MOF-based carbon capture from indoor spaces as air revitalization system

Conventional air-conditioning systems, for providing thermal comfort and acceptable indoor air quality, are energy intensive, especially for spaces located in hot and humid climates. This is attributed to the energy needed to offset the latent and sensible loads of the ambient air, which is typically achieved using a solid desiccant integrated with a vapor compression cooling. Air revitalization system (ARS) is proposed as an alternative solution to remove excess H2O and CO2 sequentially from the recirculated air using solid adsorbents such as silica gel for H2O and metal–organic frameworks (MOFs) for CO2. In this work, the feasibility of MOFs-based ARS is investigated by predicting its operational performance cost and compare it to the conventional system. Accordingly, mathematical models were developed for the adsorption beds and the indoor space and integrated to genetic algorithm. The integrated model was used to properly size and optimize the system for a classroom and a residential house located in the Qatari climate. The simulation results showed that the ARS decreased the fresh air intake by 91% and 71%, for the classroom and house, respectively, leading to savings of 30% and 24% as well as payback periods of 5 and 2 years compared to the conventional system.